1. Field of the Invention
This invention relates to a system for reproducing information signals, such as video signals, to obtain an improved signal-to-noise ratio when such signals are reproduced from a magnetic recording medium.
2. The Prior Art
In recording television signals on a magnetic medium, it has been a common practice heretofore to modulate the frequency of a relatively high frequency carrier by means of the luminance signal of the composite television signal and then to record the resulting frequency-modulated signal on the magnetic medium. The signal-to-noise (S/N) ratio of the reproduced signal can then be quite high.
However, frequency modulation requires a relatively wide frequency deviation in order to obtain the best S/N characteristics. In the case of a frequency-modulated signal recorded on magnetic tape, this leads to the further requirement that the bandwidth of the information signal be limited or that a large quantity of the magnetic medium, such as magnetic tape, discs, or sheets, be used. In recording video signals on magnetic tape, it is customary to use a drum with a rotary magnetic head and to wrap the tape at least part way around the drum. If a wide band signal is to be recorded, the relative rotation of the rotary magnetic head with respect to the tape must be increased, and accordingly, a large head drum has been required for wide band recording.
A further disadvantage of the use of frequency modulation is that such signals produce a number of harmonics which require a circuit to filter them out.
A still further difficulty that arises when a video signal is magnetically recorded by prior apparatus is that the signal is commonly recorded in a series of adjacent tracks spaced apart from each other to provide an area referred to as a guard band between them. Such guard bands use up additional recording medium, and a number of techniques have been developed to minimize the width of guard bands. However, it has been difficult to eliminate beat signals generated between adjacent tracks when the guard bands are made too narrow or are entirely eliminated.